1. Field of the Invention
The invention relates to a pipe centering apparatus used to center, on an appropriate bed or the like, metallic pipes such as aluminum pipes, plastics pipes or other pipes of a predetermined length, and more particularly the invention relates to a pipe centering apparatus used to cause such pipes to stand in row and side by side with their longitudinal centers aligned with each other while they are being transported on a conveyor or the like but before they are subjected to a cutting process or a machining process in which their end surfaces are machined or finished.
2. Description of Prior Art
In some fields of industry, there are used certain kinds of relatively short pipes which are made of for instance aluminum and to be precisely finished as to their diameter, non-eccentricity, wall thickness, straightness and other features. In general, elongate drawn pipes made by drawing raw extruded pipes are corrected of their straightness and are cut into the relatively short pipes. And, chips produced by the cutting operation and sticking to the end surfaces of short pipes are removed before edges of the end surfaces are rounded or chamfered to finish the short pipes.
The chamfering operation has been carried out for example in such a manner as shown in FIG. 5. Clampers 54 of a double-ended chamfering machine 53 hold a short pipe 52 on a conveyor 51 on which the pipe has been transported. Rotary machine tools 55 disposed on the right-hand side and left-hand side of the conveyor are then operated to rotate about their own axes and to inwardly move in a symmetrical manner towards each other. The rotary machine tools thus bear against the ends of the pipe 52 to thereby chamfer the corner portions or edges of said ends.
It is however to be noted that the short pipes 52 on the conveyor 51 are more or less at unaligned state in respect of their longitudinal positions. If the pipes in such an "irregular" state are held by the clampers 54 and are machined by the chamfering machine 53, then machining allowance or degree for one end of the pipe 52 will become different from that for the other end. This will bring about a drawback that effective machining period of time and actually machined states are different between the ends of each pipe. Further, cutting blades will be abraded to different degrees between the right and left rotary machine tools 55, thereby shortening the life of one cutting blade. In an extraordinary case, one end of the pipe 52 will remain unmachined.
In order to avoid such disadvantages, it has been required to center the pipe 52 before it is clamped by the clampers 54 of the chamfering machine 53.
Therefore, the centering of the pipes has been done using for example an apparatus 56 shown in FIG. 5. The prior art centering apparatus 56 comprises a stopper 57 on one side of the conveyor 51, and a pneumatic or hydraulic cylinder 58 on the other side of the conveyor, with the conveyor being interposed between the stopper and the cylinder which face the stopper. The stopper 57 regulates position of one end of each pipe 52 which has been transported on the conveyor to the centering apparatus 56 and is pushed towards the stopper by the cylinder, thereby centering the pipe. In the prior art centering apparatus 56 as described above, position of only one end of each cut pipe 52 is regulated so that it is difficult to accurately center all of the cut pipes 52 even in a case wherein pipe length varies very slightly between the cut pipes 52 transported to the apparatus. Particularly, in a case where an elongate drawn pipe is cut into shorter pipes to be chamfered, such a problem becomes more severe in the prior art apparatus 56 because length of the drawn elongate pipes tends to vary to a remarkable degree due to the nature of the drawing process.
Thus, the prior art apparatus 56 also fails to exactly chamfer both the ends of each cut pipe 52. The difference in the machining times and in the life of cutting blades of the rotary machine tools 55 cannot be diminished by the apparatus 56, between one end and the other end of each cut pipe.
In addition, the cylinder 58 of the prior art centering apparatus 56 pushes towards the stopper 57 the pipes 52 lying on the conveyor 51. Such a sliding contact of the pipes 52 with the conveyor 51 causes scratches of outer surfaces of the pipes.
Those scratches or flaws will be very serious defects if the pipes 52 produced by the drawing process are used as photosensitive drums which bear thereon photosensitive layers such as selenium layer or organic photoconductive layers to be installed in the electronic copiers, laser printers or the likes. Consequently, yield of acceptable products has not been satisfactorily high.